Philosophy of science and, more specifically, philosophy of quantum physics can be but special fields of a general philosophy of knowledge; and the problems arising in these fields can be evaluated properly only when they are seen under the perspective of the whole range of human knowledge. This paper deals with problems of quantum physics and, in particular, with the problem of scientific objects in quantum physics from the epistemological point of view previously defined in the author's books, A Philosophy of Science (1940) and The Basis and Structure of Knowledge (1948). The argument of the paper, however, has not been stated before in the direct and concise manner here attempted and may therefore contain elements of novelty even for those readers who are familiar with the books just mentioned.

Professor Margenau's paper presents an analysis of physical theory which has the great merit of exhibiting classical physics and modern quantum mechanics as different aspects of the same epistemological and methodological framework.

By maintaining that “there is not a tree and my construct of it, nor a wave length and my construct of it” he is denying that the constructs of ordinary common sense and, a fortiori, the theoretical constructs of the physical sciences denote entities existing independently of our rational manipulation of them. This denial then enables him to treat constructs like “tree” and “electric current” exactly on a par with the Ψ-functions of quantum mechanics not only methodologically but also ontologically. Once this is granted, he has prepared the ground for his synthesis of classical physics with quantum mechanics and is justified in inferring that “In quantum mechanics, then, the basic mode of description has remained unaltered while the rules of correspondence have undergone radical changes.”

The intention of the present essay is to urge a reconsideration of the Realism-Phenomenalism-Issue, mainly and primarily in regard to the interpretation of scientific hypotheses; secondarily also relating to the basic problems of epistemology.

History of Science is a many-sided subject, permitting approach from the point of view of various human interests, and presenting a wide variety of problems, many of them paradoxical and perhaps not capable of satisfactory solution. In the following it will probably seem to the reader a number of times that I am talking at cross purposes. Anything that I can say is of necessity limited by my background as a physicist.

1. Terminological Considerations. Since Russell enunciated the principle, “Wherever possible logical constructions are to be substituted for inferred entities,” or “Wherever possible, substitute constructions out of known entities for inferences to unknown entities,” the terminological situation has become confused. Russell defined neither “construction” nor “inferred entity.” “Construct” soon came to be used for “construction,” perhaps to avoid the ambiguity whereby the latter term was used to refer to both a process and a result. But many writers now use “construction” or “construct” to refer to what Russell called the “inferred entity.” This seems to be the usage of Margenau, Ramsperger, Benjamin, Bures, and many others. Again, some of the same writers in other places (e.g., Benjamin) remain closer to Russell's usage. And I find it difficult to determine exactly the relation of the usage of some writers to that of Russell because of the differences between their contexts and Russell's. I experience this difficulty in reading, for instance, both Miss Stebbing and Werkmeister. The terminological difficulties have been evaded by some other writers who have formulated new terms to refer to Russell's inferred entities. Thus Northrop speaks of the “theoretic component” and Miller has coined the word, “interphenomena.” The terms reflecting Russell's rule in psychology have become so confused that a set of explicit definitions has recently been proposed.

It has been questioned whether it is at all possible to give the term “probability” one uniform and consistent interpretation not merely in mathematics, statistics, evaluation of evidence, testing of hypotheses but also in any situation where we want to express a degree of belief. The question itself of assigning a probability to our belief in a scientific theory has raised important questions of an epistemological as well as mathematical nature.

The position that science is a technique establishing the means to achieve any stipulated end has now fanned out and been defended by social scientists as well as by natural scientists. It is the thesis of this paper that the bifurcation of science and morality derives from the social status of both science and scientists today, and involves, wittingly or unwittingly, an uncritical acceptance of dominant social values. Science is thus not non-moral, as is claimed, but rather appropriates conventional morality. Certain conditions have brought about this role for science and scientists.

“We are in the position of a little child,” said Einstein in a press interview twenty years ago, “entering a huge library whose walls are covered to the ceiling with books in many different tongues. … The child does not understand the languages in which they are written. He notes a definite plan in the arrangement of the books, a mysterious order which he does not comprehend, but only dimly suspects.”